Grease and method of preparation



Patented Jan. 17, 1939 GREASE AND METHOD OF PREPARATION Eger V. Murphree, Summit, and William J. Sweeney, Elizabeth, N. 3%, assignors to Stand and Oil Development @ompany, a corporation of Delaware No Drawing.

Application December 30, 1933, Se-

rial No. 704,748. Renewed June 29, 1938 6 Claims.

This invention relates to the preparation of improved, normally solid lubricants, such as greases, consisting primarily of a mixture of suitable oils and normally solid soaps, suitable for lubrication of bearings operated at high temperatures and pressures, and to the improved compositions obtained thereby. This invention relates more particularly to methods for preparing driving journal compounds and similar greases of improved texture, feel, moldability and plasticity, and of increased stability in use at elevated temperatures, say 250 to 300 F. or higher. It has long been known to be desirable to prepare such greases in as nearly an anhydrous state as possible since even a small amount of water causes the grease to fan out of bearings operated at temperatures above about 212 F., probably due to vaporization resulting in an enormous increase in the volume occupied by the water present. Substantially anhydrous greases may be prepared by carefully heating suitable oils, such as steam refined cylinder oil, and suitable soaps such as sodium soaps of tallow acids, to a temperature of about 400 to 500 F. or somewhat higher. However, the greases thus prepared are objectionably crumbly and have a poor texture and are not readily molded into cakes,

the form in which they are applied to journals.

It has now been found that substantially anhydrous greases of proper texture and moldability may be obtained by the addition of suitable modifying and plasticizing agents. is a controlled small amount of glycerine. The amount of glycerine used will vary somewhat in relation to the composition of the grease, but will in all events be less than an equivalent amount to the glycerides of the acids used in preparing the soap component of the grease.

With ordinary greases containing about 40 to 50% of a steam refined cylinder oil or equivalent hydrocarbon oil, and about 40 to 50% of the sodium soap of tallow acids, the use of about /2 to 3% of glycerine is desirable, and about 2% by weight of glycerine in the finished composition is generally preferable. The use of larger amounts of glycerine renders the finished grease unstable at elevated temperatures; for example, greases similar to the above but containing about 4% of glycerine (as obtained by saponification during the cooking of the grease when tallow is used as the only source of soap acids) show a substantial seepage of oil from the grease cake when exposed for a long time to a temperature of about 300F. This seepage or bleeding, in

One such agent addition to representing a loss of lubricant, is also objectionable because it causes a non-uniform composition of the grease cake, resulting in improper lubrication.

It has also been found that the addition of small amounts of oxygenated pitches to ordinary,

V grease compositions improves the appearance and texture of the grease. Such oxygenated pitches may be obtained by polymerization or thickening of vegetable oils and their corresponding fatty acidsand esters. Cottonseed oil pitch, the resi due on distillation of black grease obtained from cottonseed foots, is an example of one type of pitchsuitable for this invention. Other examples are soft stearine pitch and the residue obtained in distilling natural and synthetic fatty acids, such as those obtained by limited oxidation of parafiine wax. While the precise composition has not been determined, it is believed that such residues contain highly polymerized acids and lactones together with other oxygen containing organic compounds.

The pitches preferred for use according to this invention are those semi-solid,sticky,plastic,nondistillable oxygen containing polymerization and condensation products of vegetable oils, and corresponding fatty acids (natural or synthetic) and esters of such acids, which are soluble or readily miscible in the oily component of the grease at temperatures below about 200 F. It is ordinarily desirable to use from 1 to of such pitches in the grease, although greater or smaller amounts may be used.

Greases prepared according to this invention may contain the controlled amount of glycerine described above, or pitch, together or separately. Best results, however, will be obtained by using both glycerine and pitch in the grease preparation.

The following example is presented to illustrate one suitable method for preparing greases according to this invention and the products obtained thereby:

Heat 51% pounds of a steam refined cylinder oil, of 190 to 210 seconds Saybolt viscosity at 210 F., to about 160 F. and add 3 pounds of cottonseed oil pitch (86 F. melting point) with stirring until complete mixing is obtained. Then add 21.9 pounds'of free tallow acids and pounds of prime tallow, with stirring. Then add slowly with constant stirring a 40 Baum aqueous solution containing 6.65 pounds of caustic soda while maintaining the mixture at a temperature of 160 to 165 F. When the addition of the caustic soda is completed, the mixture is heated slowly to 225 F., at which temperature water begins to' steam off and frothing is apt to occur. The rate of heating is thereafter determined by the extent of frothing, which ordinarily lasts about one hour when the grease cooks down at a temperature of about 255 F.

The mixture is then heated rapidly to 500 F. and maintained at this temperature for about 1 hours or until the moisture content of the grease is less than 1% and is preferably below 0.5 to 0.3%. The cooked grease is then Withdrawn from the bottom of the heated vessel into suitable receptacles or molds, in which it is allowed to cool and solidify. The best structure of grease will be obtained by allowing the grease to cool with agitation to just above the temperature at which solidification begins, before the grease is drawn into molds.

The composition of the resulting grease is as This invention is not to be limited by any specific examples which have been presented herein solely for the purpose of illustration but only by the following claims, in which it is desired to claim all novelty in so far as the prior art permits.

We claim:

1. A grease composition consisting principally of substantially equal amounts of soap and heavy hydrocarbon oil and containing glycerine in an appreciable amount but less than the equivalent of the glyceride of the acid component of said soap, and not more than about 10% of an oxygenated pitch miscible with said oil.

2. Composition according to claim 1 containing more than each of said soap and said oil.

3. Composition according to claim 1, containing more than 40% each of said soap and said oil,

and in which the content of glycerine is from 72% to 3% by weight.

4. Substantially anhydrous non-bleeding grease consisting principally of approximately equal amounts of heavy hydrocarbon oil and normally solid soap of a fatty acid, and containing glycerine in an amount below about 3% and not more than about 10% of a fatty acid pitch.

5. Substantially anhydrous non-bleeding grease consisting principally of approximately equal amounts of heavy hydrocarbon oil and a normally solid soap of a fatty acid, about 2% of glyceririe and from 1-5% of fatty acid pitch.

6. A composition according to claim 5 in which the fatty acid pitch is cotton seed oil pitch.

EGER V. MURPHREE. WILLIAM J. SWEENEY. 

